1. Field of the Invention
The present invention relates to a focus detection device for an image forming optical system, an imaging apparatus, and a focus detection method for an image forming optical system.
2. Description of Related Art
Japanese Laid Open Patent Publication No. 2007-011314 discloses an image forming state detection device that includes two-dimensionally arrayed micro-lenses with a plurality of light-receiving elements (photoelectric conversion units) disposed in correspondence to each micro-lens. This image forming state detection device extracts a pair of signal strings corresponding to images formed with light fluxes having passed through different areas on pupil of the image forming optical system based upon light reception outputs obtained at the plurality of light-receiving elements. The image forming state detection device then determines the image forming state at the image forming optical system by detecting an offset between the phases of the signal string pair having been extracted.